The present invention relates to a finger-touch coordinate input apparatus of a touch screen system, which allows direct information input to an information processing apparatus from a coordinate position on a display screen by pointing out a desired position on a display of a cathode ray tube (CRT) display device (or some other like device).
As a coordinate input apparatus of a touch screen system of this type, the following two systems are generally well known in the art. A first system includes a touch pad which is adhered to a display screen, such as a tube surface of a CRT display device, and a capacitance change (i.e., a parameter change) caused by pressing a predetermined point of the pad with a finger tip is detected, thereby determining a coordinate position. In a second system, a plurality of opposite light-emitting and light-receiving element pairs are arranged along upper, lower, right, and left side edges of a tube surface (display screen) of a CRT display device to obtain a matrix-like optical path, whereby light-receiving states along the X- and Y-axes are scanned, thereby determining a coordinate position pointed out by a finger tip from a shielded, or interrupted, light path. In the later optical system using the above-mentioned light-emitting and light-receiving elements, unlike the former system, a display screen is not pressed directly by a finger or other pointed object, so that the screen is not contaminated by dirt and the image on the screen remains clear, resulting in greater practical advantages.
In the conventional optical finger-touch coordinate input apparatus described above, dust enters, falls, and is deposited on the parts of the light-emitting elements (or light-receiving elements) constituting photodetectors arranged along and inside the side edges of the display screen, or dust (or the like) tends to be adhered to the back surfaces of the LED filters, thereby degrading a light-emitting or light-receiving function. This problem is significant because the printed circuit boards and the LED filters constituting the photodetectors described above are disposed on a curved surface of the display screen of the CRT display device so that the space in this portion cannot be eliminated. In addition, dust tends to adhere to the surface of the above-mentioned display screen because of a high voltage of the CRT display device.
To eliminate such an operational failure, periodical cleaning is required. However, since the above-mentioned light-emitting and light-receiving elements are disposed inside the housing, the cleaning is troublesome, complex, and hence is not practical. Therefore, an easy and proper countermeasure is needed to eliminate the functional failure due to disposition of dust or the like, with a simple arrangement.
In order to eliminate the above problem, a finger-touch coordinate input apparatus according to the present invention comprises printed circuit boards provided between a display screen and its front frame and having light-emitting and light-receiving element groups thereon, and LED filters provided outside the printed circuit boards at a predetermined distance therefrom, constituting side edges of the display screen, and having light-transmitting portions in parts thereof, wherein spaces formed between the printed circuit boards and the LED filters are connected to an air supply source so that an air flow is generated in at least one of the spaces, thereby effectively eliminating the deposition or adhesion of dust to the light emitting and light receiving elements.